Remove reference to libpeerconnection from sizes.py
Remove reference to libpeerconnection from sizes.py

This library is now statically compiled into the main Chrome binary.

BUG=482123
TESTED=None, but I verified that there's nothing printed in the sizes steps on the bots at http://build.chromium.org/p/chromium/waterfall

Review URL: https://codereview.chromium.org/1400533002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@297088 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build